I know this is not a mustang question, but I have an 1990 f-250 with the stock 351w and auto transmission in it and the problem is that under mild acceleration it sputters until i get above 2500 RPMs. Also it shakes alot when i am at a stop light in Drive but if i put it in nuetral it ideals great with no shaking. Any ideas?

 

Sounds like plug wires to me, they will do fine without a load,put the least load on
thenthey misfire. One wire could be hanging loose orout of timing order. Check at night,
have some one sit in the truck and go from Drive to neutral, if bad normally you will see the
little blue sparks jumping to ground.Cant see themif not dark under the hood, If so
replace the plugwires, if that doesn't do it. Next would be the coil.Good luck

Ray

 

I tried that and everything checks out. It only happens between 1000rpm and 2500rpm. I am thinking timming chain?

 

I've got a 93 f-250 with a 351. I was having issue's similar to your's actually i still am. Mine would do what yours doe's and the tranny would kick down at time's when i did not think it should. When it did this it would rumble. I drained what fluid i could out of the tranny pan and put in a new filter. That corrected the problem for a year and now it has started again. I'm sure mine is tranny related because the engine was replaced a few months ago with a reman with a 3 year unlimited mileage warranty. It came with new timing chain and everything else, i just had to re-use my manifold and oil pan.

 

Wow, o.k ,I will try that. Alot less work than timming chain. Thanks everyone.